diff -r 000000000000 -r 6474c204b198 webapprt/DirectoryProvider.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/webapprt/DirectoryProvider.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,56 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+const Cc = Components.classes;
+const Ci = Components.interfaces;
+const Cu = Components.utils;
+
+const WEBAPP_REGISTRY_DIR = "WebappRegD";
+const NS_APP_CHROME_DIR_LIST = "AChromDL";
+
+Cu.import("resource://gre/modules/FileUtils.jsm");
+Cu.import("resource://gre/modules/XPCOMUtils.jsm");
+Cu.import("resource://webapprt/modules/WebappRT.jsm");
+Cu.import("resource://gre/modules/Services.jsm");
+
+function DirectoryProvider() {}
+
+DirectoryProvider.prototype = {
+  classID: Components.ID("{e1799fda-4b2f-4457-b671-e0641d95698d}"),
+
+  QueryInterface: XPCOMUtils.generateQI([Ci.nsIDirectoryServiceProvider,
+                                         Ci.nsIDirectoryServiceProvider2]),
+
+  getFile: function(prop, persistent) {
+    if (prop == WEBAPP_REGISTRY_DIR) {
+      let dir = Cc["@mozilla.org/file/local;1"].createInstance(Ci.nsILocalFile);
+      dir.initWithPath(WebappRT.config.registryDir);
+      return dir;
+    }
+
+    // We return null to show failure instead of throwing an error,
+    // which works with the way the interface is called (per bug 529077).
+    return null;
+  },
+
+  getFiles: function(prop, persistent) {
+    if (prop == NS_APP_CHROME_DIR_LIST) {
+      return {
+        _done: false,
+        QueryInterface: XPCOMUtils.generateQI([Ci.nsISimpleEnumerator]),
+        hasMoreElements: function() {
+          return !this._done;
+        },
+        getNext: function() {
+          this._done = true;
+          return FileUtils.getDir("AppRegD", ["chrome"], false);
+        }
+      };
+    }
+
+    return null;
+  },
+};
+
+this.NSGetFactory = XPCOMUtils.generateNSGetFactory([DirectoryProvider]);